Enabling IAP for App Engine

This page explains how to secure an App Engine instance with Identity-Aware Proxy (IAP).

Before you begin

To enable IAP for App Engine, you need the following:

A Google Cloud console project with billing enabled.

If you don't have your App Engine instance set up already, see Deploying App Engine for a complete walkthrough.

IAP uses a Google-managed OAuth client to authenticate users. Only users within the organization can access the IAP-enabled application. If you want to allow access to users outside of your organization, see Enable IAP for external applications.

Enabling IAP

Console

The Google-managed OAuth client is not available when enabling IAP using the Google Cloud console.

Dynamic include file

If you haven't configured your project's OAuth consent screen, you'll be prompted to do so. To configure your OAuth consent screen, see Setting up your OAuth consent screen.

Setting up IAP access

Go to the Identity-Aware Proxy page.
Go to the Identity-Aware Proxy page
Select the project you want to secure with IAP.
Select the checkbox next to the resource you want to grant access to.
On the right side panel, click Add principal.
In the Add principals dialog that appears, enter the email addresses of groups or individuals who should have the IAP-secured Web App User role for the project.
The following kinds of principals can have this role:
- Google Account: user@gmail.com
- Google Group: admins@googlegroups.com
- Service account: server@example.gserviceaccount.com
- Google Workspace domain: example.com
Make sure to add a Google Account that you have access to.
Select Cloud IAP > IAP-secured Web App User from the Roles drop-down list.
Click Save.

Turning on IAP

On the Identity-Aware Proxy page, under APPLICATIONS, find the application you want to restrict access to. To turn on IAP for a resource,
In the Turn on IAP window that appears, click Turn On to confirm that you want IAP to secure your resource. After you turn on IAP, it requires login credentials for all connections to your load balancer. Only accounts with the IAP-Secured Web App User role on the project will be given access.

gcloud

Before you set up your project and IAP, you need an up-to-date version of the gcloud CLI. For instructions on how to install the gcloud CLI, see Install the gcloud CLI.

To authenticate, use the Google Cloud CLI and run the following command.
```
gcloud auth login
```
Click the URL that appears and sign in.
After you sign in, copy the verification code that appears and paste it in the command line.
Run the following command to specify the project that contains the applications that you want to protect with IAP.
```
gcloud config set project PROJECT_ID
```

To enable IAP, run the following command.

gcloud iap web enable --resource-type=app-engine --versions=version

Add principals who should have the IAP-secured Web App user role to the project.
```
gcloud projects add-iam-policy-binding PROJECT_ID \
       --member=PRINCIPAL_IDENTIFIER \
       --role=roles/iap.httpsResourceAccessor
```
- Replace PROJECT_ID with your project ID.
- Replace PRINCIPAL_IDENTIFIER with the necessary principals. This can be a type of domain, group, serviceAccount, or user. For example, user:myemail@example.com.

After you enable IAP, you can use the gcloud CLI to modify the IAP access policy using the IAM role roles/iap.httpsResourceAccessor. Learn more about managing roles and permissions.

API

Run the following command to prepare a settings.json file.

cat << EOF > settings.json
{
"iap":
  {
    "enabled":true
  }
}
EOF

Run the following command to enable IAP.

curl -X PATCH \
-H "Authorization: Bearer $(gcloud auth print-access-token)" \
-H "Accept: application/json" \
-H "Content-Type: application/json" \
-d @settings.json \
"https://appengine.googleapis.com/v1/apps/PROJECT_ID?updateMask=iap"

After you enable IAP, you can use the Google Cloud CLI to modify the IAP access policy using the IAM role roles/iap.httpsResourceAccessor. Learn more about managing roles and permissions.

Test user authentication

Access the app URL from a Google account that you added to IAP with the IAP-secured Web App User role as described above. You should have unrestricted access to the app.
Use an incognito window in Chrome to access the app and sign in when prompted. If you try to access the app with an account that isn't authorized with the IAP-secured Web App User role, you'll see a message saying that you don't have access.